The invention relates to a method for sensorless commutation identification in electronically commutated electric motors.
In electronically commutated DC electric motors, the magnetic rotating field that is required for the rotary movement is controlled by electronics. The commutation times are dependent on the rotor position of the motor and can either be picked up by sensor or determined by measuring the mutual induction voltage. In order to detect the zero crossings, comparators are used and the comparator signals are evaluated by microcontroller.
Prior art FIG. 1 shows a block diagram of an electric motor 10 and a controller 12 that controls the electric motor.
Detection of the zero crossing requires the associated phase not to be supplied with current for a defined period in order to avoid covering the induced voltage. This so-called blanking gap, during which no current is supplied, needs to be chosen to be large enough to rule out the induced voltage being covered in different operating states of the motor. However, larger blanking gaps have an adverse effect on noise and power.